The present invention relates to particles in capsule form that contain finely particulate bleaching agent in their interior and whose matrix capsule material is a crosslinked polymer, and to methods for their manufacture; and in particular to liquid water-containing laundry detergents and cleaning agents that contain such particles.
In laundry detergents and cleaning agents in liquid form, especially when they contain water but also when they are anhydrous, chemical incompatibility of the individual ingredients can result in negative interactions among said ingredients, and in a decrease in their activity and thus a decrease in the washing performance of the detergent or agent as a whole, even if it is stored for only a relatively short time. This decrease in activity affects, in principle, all laundry-detergent ingredients that perform chemical reactions in the washing process in order to contribute to the washing result, in particular bleaching agents and enzymes, although surfactant or sequestering ingredients that are responsible for dissolution processes or complexing steps also do not have unlimited shelf stability in liquid systems, in particular aqueous systems, especially in the presence of the aforesaid chemically reactive ingredients.
Among the bleaching agents, phthalimidoperoxyalkanoic acids such as, for example, 6-phthalimidoperoxyhexanoic acid (PAP) are known to be highly efficient, but they are particularly unstable chemically in conventional liquid laundry-detergent formulations. In the latter, they usually decompose completely in a few days. Even if possible reaction partners for the peroxycarboxylic acids, such as unsaturated compounds, aldehydes, amines, chloride, etc., are removed from these liquid detergents, they nevertheless decompose in the presence of the surfactants, even when the latter are not oxidatively attacked. The reason for this is possibly that the phthalimidoperoxyalkanoic acids, constituting solids having low water solubility, are stable in that form, but they dissolve in the presence of surfactants, are highly reactive in dissolved form, and decompose both via a bimolecular reaction with the release of singlet oxygen and by hydrolysis yielding phthalimidoalkanoic acid and H2O2. The latter, however, has practically no bleaching activity especially at low washing temperatures and in the resulting concentrations, with the result that storage causes the bleaching action of the detergent to be lost.
The consumer, however, demands liquid laundry detergents and cleaning agents that have an optimal effect at the time of utilization even after storage and transport. This requires that the ingredients of the liquid laundry detergent and cleaning agent not have previously diminished, decomposed, or volatilized.
The loss of volatile components, for example, can be prevented by way of complex and correspondingly expensive packages. Chemically incompatible components can be stored separately from the remaining components of the liquid laundry detergent and cleaning agent and then metered in for use. The utilization of opaque packaging prevents the decomposition of light-sensitive components, but also has the disadvantage that the consumer cannot see the appearance and quantity of the liquid laundry detergent and cleaning agent.
One concept for the incorporation of sensitive, chemically or physically incompatible, and volatile ingredients consists in the use of capsules in which said ingredients are enclosed. A distinction is made between two types of capsules: on the one hand there are capsules having a core-shell structure, in which the ingredient is surrounded by a wall or barrier. On the other hand there are capsules in which the ingredient is distributed in a matrix made of a matrix-forming material. Such capsules are also referred to as “speckles.”
When capsules and other particles are used in laundry detergents, it is also important that they dissolve during the washing operation and leave no residues on the laundry. The same applies analogously to the use thereof in cleaning agents for hard surfaces.
It has occasionally also been proposed to solve the problem of the insufficient stability of bleaching agents, and in particular of peroxycarboxylic acids, by way of a coating. European Patent EP 0 510 761 B1, for example, has described a coated bleaching agent granulate that comprises, as an encasing material, paraffin having a melting point in the range from 40° C. to 50° C., mixed with specific additives selected from ethylene/vinyl acetate copolymers, hydrogenated colophony methyl esters, ethyl acrylate/2-ethylhexyl acrylate copolymers, and mixtures thereof. European Patent Application EP 0 436 971 A2 discloses encased particles that comprise 45 to 65 wt % of a solid bleaching-agent-containing core and 35 to 55 wt % of an encasing layer that contains paraffin wax having a melting point in the range from 40° C. to 50° C. Imidoperoxycarboxylic acids are not listed therein under the bleaching agents. It has been shown, however, that the application of coating materials does not by any means always lead to an increase in the stability specifically of highly active bleaching agents such as, for example, imidoperoxycarboxylic acids.
U.S. Pat. No. 6,855,681 discloses a cleaning-agent composition that encompasses a matrix-encapsulated active ingredient. The matrix of the capsules contains a hydrated anionic gum, and the encapsulated active ingredient is by preference a fragrance.